The present invention relates to apparatus for and a method of anchoring an expandable conduit, particularly, but not exclusively, to a second conduit in which the expandable conduit is located.
A borehole is conventionally drilled during the recovery of hydrocarbons from a well, the borehole typically being lined with a casing that is cemented into place. Casings are installed to prevent the formation around the borehole from collapsing. In addition, casings prevent unwanted fluids from the surrounding formation from flowing into the borehole, and similarly, prevent fluids from within the borehole escaping into the surrounding formation.
It is known to use a pliable casing that can be radially expanded so that an outer surface of the casing contacts the formation around the borehole. The pliable casing undergoes plastic deformation when expanded, typically by passing an expander device, such as a ceramic or steel cone or the like, through the casing. The expander device is propelled along the casing in a similar manner to a pipeline pig and may be pushed (using fluid pressure for example) or pulled (using drill pipe, rods, coiled tubing, a wireline or the like).
Lengths of expandable casing are coupled together (typically by threaded couplings) to produce a casing string. The casing string is inserted into the borehole in an unexpanded state and is subsequently expanded using the expander device. However, the unexpanded casing string requires to be anchored either at an upper end or a lower end thereof before and/or during the expansion process.
According to a first aspect of the present invention, there is provided apparatus for anchoring an expandable conduit, the apparatus comprising at least one formation provided on an outer surface of the expandable conduit, the formation being capable of engaging a second conduit in which the expandable conduit is located, the formation providing an anchor and/or seal for the expandable conduit when the expandable conduit is at least partially expanded.
According to a second aspect of the present invention, there is provided a method of anchoring an expandable conduit, the method comprising the steps of providing an expandable conduit having at least one formation on an outer surface thereof, the formation being capable of engaging a second conduit in which the expandable conduit is located to provide an anchor and/or seal for the expandable conduit, anchoring the expandable conduit to the second conduit, and expanding at least a portion of the expandable conduit to force the formation into contact with the second conduit.
The invention also provides expandable conduit such as casing or the like, the conduit having a formation on its outer surface adapted to engage a second member when the expandable conduit is expanded.
The formation typically comprises resilient material, typically first and second bands of a first resilient material such as rubber, the first and second bands being axially spaced apart, with a third band of a second resilient material such as a second rubber being located between the first and second bands. The first material is preferably harder than the second material. The first and/or second materials may be profiled on an outer surface thereof to enhance anchoring and/or sealing.
In one specific embodiment of the invention, the first and second bands comprise 2 inch (approximately 51 millimeters) wide bands, spaced apart by 10 inches (approximately 250 millimeters). The third band typically comprises a 10 inch (approximately 250 millimeters) wide band. The first rubber is typically a 60 durometer rubber. The second rubber is typically a 40 durometer rubber. The bands of rubber can be of any suitable hardness and width. Alternatively, the first rubber can be a 90 durometer rubber, and the second rubber can be a 60 durometer rubber.
In an alternative embodiment, the formation comprises a band of rubber or other suitable resilient material. The band preferably defines a zigzag pattern on the outer surface of the conduit. The rubber can be of any suitable hardness, but is typically in the order of 40 to 90 durometers, although values of hardness outwith this range may also be used.
The material properties and configuration of the or each formation can be chosen to suit the particular application.
The expandable conduit typically comprises an expandable casing or liner. However, the expandable conduit may be any suitable expandable pipe or the like.
The formation is optionally detachable and preferably applied to the outer surface of the conduit before the conduit is expanded. The formation optionally comprises two or more axially spaced formations.
The second conduit typically comprises a borehole, casing, liner or the like. The expandable casing may engage any type of conduit.
The method of the invention typically includes the additional step of providing an expander device to radially expand the expandable conduit.
The expander device typically comprises a cone. The expander device may be manufactured from steel. Alternatively, the expander device may be manufactured from a ceramics material, or a combination of steel and a ceramics material. The expander device is optionally flexible.
The expandable conduit is typically temporarily anchored to the second conduit using a mechanical or other anchoring device (e.g. a slip).